CATV networks use an infrastructure of interconnected coaxial cables, signal splitters and combiners, repeating amplifiers, filters, trunk lines, cable taps, drop lines and other signal-conducting devices to supply and distribute high frequency “downstream” signals from a main signal distribution facility, known as a “headend,” to the premises (homes and offices) of CATV subscribers. The downstream signals operate the subscriber equipment, such as television sets, telephone sets and computers. In addition, most CATV networks also transmit “upstream” signals from the subscriber equipment back to the headend of the CATV network. For example, the subscriber uses a set top box to select programs for display on the television set. As another example, two-way communication is essential when using a personal computer connected through the CATV infrastructure to the public Internet. As a further example, voice over Internet protocol (VOIP) telephone sets use the CATV infrastructure and the public Internet as the communication medium for transmitting two-way telephone conversations.
To permit simultaneous communication of upstream and downstream CATV signals and the interoperability of the subscriber equipment and the equipment associated with the CATV network infrastructure outside of subscriber premises, the downstream and upstream signals are confined to two different frequency bands. The downstream frequency band is within the range of 54-1002 megahertz (MHz) and the upstream frequency band is within the range of 5-42 MHz, in most CATV networks.
The downstream signals are delivered from the CATV network infrastructure to the subscriber premises at a CATV entry adapter, which is also commonly referred to as an entry device, terminal adapter or a drop amplifier. The entry adapter is a multi-port device which connects at an entry port to a CATV drop cable from the CATV network infrastructure and which connects at a multiplicity of other distribution ports to coaxial cables which extend throughout the subscriber premises to a cable outlet. Each cable outlet is available to be connected to subscriber equipment. Typically, most homes have coaxial cables extending to cable outlets in almost every room, because different types of subscriber equipment may be used in different rooms. For example, television sets, computers and telephone sets are commonly used in many different rooms of a home or office. The multiple distribution ports of the entry adapter deliver the downstream signals to each cable outlet and conduct the upstream signals from the subscriber equipment through the entry adapter to the drop cable and the CATV infrastructure.
In addition to television sets, computers and telephones, a relatively large number of other entertainment and multimedia devices are available for use in homes. For example, a digital video recorder (DVR) is used to record broadcast programming, still photography and moving pictures in a memory medium so that the content can be replayed on a display or television set at a later time selected by the user. As another example, computer games are also played at displays or on television sets. Such computer games may be those obtained over the Internet from the CATV network or from media played on play-back devices connected to displays or television sets. As a further example, receivers of satellite-broadcast signals may be distributed for viewing or listening throughout the home. These types of devices, including the more-conventional television sets, telephone sets and devices connected to the Internet by the CATV network, are generically referred to as multimedia devices.
The desire to use multimedia devices at multiple different locations within the home or subscriber premises has led to the creation of the Multimedia over Coax Alliance (MoCA). MoCA has developed specifications for products to create an in-home entertainment network for interconnecting presently-known and future multimedia devices. A MoCA in-home network uses the subscriber premise or in-home coaxial cable infrastructure originally established for distribution of CATV signals within the subscriber premises, principally because that coaxial cable infrastructure already exists in most homes and is capable of carrying much more information than is carried in the CATV frequency bands. A MoCA network is established by connecting MoCA-enabled or MoCA interface devices at the cable outlets in the rooms of the subscriber premises. These MoCA interface devices implement a MoCA communication protocol which encapsulates the signals normally used by the multimedia devices within MoCA signal packets and then communicates the MoCA signal packets between other MoCA interfaces devices connected at other cable outlets. The receiving MoCA interface device removes the encapsulated multimedia signals from the MoCA signal packets, and delivers the multimedia signals to the connected display, computer or other multimedia device from which the content is presented to the user.
Each MoCA-enabled device is capable of communicating with every other MoCA-enabled device in the in-home or subscriber premises MoCA network to deliver the multimedia content throughout the home or subscriber premises. The multimedia content that is available from one multimedia device can be displayed, played or otherwise used at a different location within the home, without having to physically relocate the originating multimedia device from one location to another within the subscriber premises. The communication of multimedia content is considered beneficial in more fully utilizing the multimedia devices present in modern homes.
Since the operation of the subscriber premises MoCA network must occur simultaneously with the operation of the CATV services, the MoCA signals utilize a frequency range different from the frequency ranges of the CATV upstream and downstream signals. The typical MoCA frequency band is 1125-1525 MHz. This so-called D band of MoCA signals is divided into eight different frequency ranges, D1-D8, and these eight different D frequency ranges are used to assure communication between the selected MoCA-enabled devices. For example, the D-1 band at 1125-1175 MHz may be used to communicate CATV television programming content between a MoCA interface device associated with a set-top box in a main room of the house and another MoCA interface device connected to a television set in bedroom of the house, while a MoCA interface device connected to a computer gaming multimedia device in a basement room of the house simultaneously communicates computer game content over the D-6 band at 1375-1425 MHz to another MoCA interface device associated with a computer located in a recreation room of the house. The MoCA frequency band also includes other frequency ranges, but the D band is of major relevance because of its principal use in establishing connections between the MoCA interface devices.
Although using the subscriber premises coaxial cable infrastructure as the communication medium substantially simplifies the implementation of the MoCA network, there are certain disadvantages to doing so. The MoCA signals have the capability of passing through the CATV entry device and entering the CATV network infrastructure where those MoCA signals may then pass through a drop cable and enter another subscriber's premises. The presence of the MoCA signals at an adjoining subscriber's premises compromises the privacy and security of the information originally intended to be confined only within the original subscriber premises. The MoCA signals from the original subscriber premises which enter through the CATV network to another subscriber premises also have the potential to adversely affect the performance of a MoCA network in the other subscriber premises. The conflict of MoCA signals from the original and other subscriber premises may cause the MoCA interface devices to malfunction or not operate properly.
CATV networks are subject to adverse influences from so-called ingress noise which enters the CATV network from external sources, located at the subscriber premises. The typical range of ingress noise is in the frequency band of 0-15 MHz, but can also exist in other upstream or downstream frequencies. Ingress noise mitigation devices have been developed to suppress or reduce ingress noise from the subscriber premises in the 0-42 MHz frequency band, but the 1125-1525 MHz signals in the MoCA frequency range are considerably outside the range of the normal ingress noise. Therefore, typical ingress noise suppression devices are ineffectual in inhibiting MoCA signals.
MoCA signals, residing outside of the CATV signal frequency bands of 5-42 MHz and 54-1002 MHz, may constitute another source of noise for the CATV network. Separate MoCA frequency rejection filters have been developed for external connection to CATV entry adapters, in an effort to keep the MoCA frequency signals confined to the subscriber premises. However, the use of such devices is subject to unauthorized removal, tampering, negligence in original installation, and physical exposure which could lead to premature failure or malfunction.
Problems also arise because the CATV network and the in-home cable infrastructure were originally intended for the distribution of CATV signals. The typical in-home cable infrastructure uses signal splitters to divide a single CATV downstream signal into multiple CATV downstream signals and to combine multiple CATV upstream signals into a single CATV upstream signal. The CATV entry adapter was not originally intended to communicate MoCA signals between its active ports, as is necessary to achieve MoCA signal communication in the MoCA network. To implement the MoCA network, the MoCA signals must traverse or “jump” between separate signal component legs of a signal splitter/combiner which are connected to the multiple active ports. This signal traversal is referred to as “splitter jumping.”
The typical signal splitter has a high degree of signal rejection or isolation between its separate signal component legs. When the MoCA signals jump or traverse between the separate signal component legs of the splitter, the degree of signal rejection or isolation greatly attenuates the strength of the MoCA signals. The physical MoCA signal communication paths are also variable because of unpredictable differences in the in-home cable infrastructure. The MoCA communication protocol recognizes the possibility of variable strength MoCA signals and provides a capability to boost the strength of MoCA signals to compensate for the variable strength of the MoCA signals that would otherwise be communicated between MoCA-enabled devices.
The strength or power of the MoCA signals can be substantially greater than the strength or power of the CATV signals communicated within the subscriber premises. The higher power MoCA signals may result from the MoCA devices compensating for reduced signal strength by boosting the strength or power of the transmitted MoCA signals, or from the simple fact that the MoCA signals traverse a considerably shorter signal path within the subscriber premises MoCA network compared to the considerably longer signal path which CATV downstream signals traverse over the CATV network infrastructure. Consequently, the MoCA signals have the capability of adversely affecting the proper functionality of CATV subscriber equipment.
One example of the significant negative impact from MoCA signals occurs in a CATV entry adapter of the type which has both a passive signal distribution port and multiple active signal distribution ports. Such a CATV entry adapter supplies a passive CATV downstream signal to the passive port and receives a passive CATV upstream signal from the eMTA device connected to the passive port. The CATV entry adapter also supplies active CATV downstream signals to each of its multiple active ports and receives active CATV upstream signals from each of its multiple active ports. Such an entry adapter includes a splitter which divides the CATV downstream signals into passive signals and active signals. The passive signals are conducted through the entry adapter without amplification, conditioning or modification before they are delivered from the passive port to subscriber equipment. The active signals are usually conducted through a forward path amplifier, where the amplifier amplifies the strength of the CATV downstream signals, or modifies or conditions some characteristic of those CATV signals, before delivering them from the active ports to the active subscriber equipment. Most subscriber equipment benefits from amplified CATV downstream signals. The majority of ports on a CATV entry adapter are active ports. Usually only one passive port is provided for each entry adapter.
The subscriber equipment connected to the passive port of the entry adapter is an embedded multimedia terminal adapter (eMTA) device, typically a “lifeline” telephone set. An eMTA device combines a cable modem and analog telephone adapter. The cable modem provides a data interface for communicating Internet protocol packets to and from the CATV network, and an analog telephone adapter provides a voice over Internet protocol (VoIP) interface for the analog telephone set. The eMTA device converts between analog voice signals and packets. A lifeline telephone is a well known example of an eMTA device.
The passive signals conducted through the entry adapter do not undergo amplification, conditioning or modification in the entry adapter before they are delivered from the passive port to passive eMTA subscriber equipment. In general, the passive signals are intended to remain available and useful in emergency conditions. The functionality of a lifeline telephone set can not depend on the proper functionality of an amplifier or other active signal conditioner in the passive signal path. Consequently, the passive CATV downstream signals received by the eMTA lifeline telephone device have relatively low power, compared to the power of the MoCA signals communicated between the MoCA devices connected to the active ports of the entry adapter.
The entry adapter includes an upstream bandpass filter which conducts the CATV upstream signals in the 5-42 MHz frequency band and a downstream bandpass filter which conducts the CATV downstream signals in the 54-1002 MHz frequency band. Although the CATV upstream and downstream bandpass filters are intended to substantially reject signals outside of their bandpass frequencies, the substantially higher power MoCA signals in the 1125-1525 MHz frequency band have the capability of bleeding through typical CATV upstream and downstream bandpass filters with sufficient strength to rival or predominate over the strength of the CATV downstream passive signals delivered from the passive port to the eMTA subscriber equipment. The MoCA signals are noise to the eMTA subscriber equipment, and the eMTA subscriber equipment does not function in response to MoCA signals. However, the strength of the MoCA signals can constitute such a significant noise level as to overwhelm or overdrive the eMTA device and thereby degrade or interfere with its functionality to the point where reliable communication cannot be achieved. It is for this reason that CATV entry adapters which also serve as part of the MoCA network are subject to requirements for MoCA signal isolation or rejection at the passive port compared to the active and entry ports of the entry adapter. At the present time, passive port isolation of approximately 60 dB is considered desirable.
The problem of the power from MoCA signals interfering with the proper functionality of eMTA subscriber equipment connected to the passive port of a CATV entry adapter only occurs with respect to subscriber equipment which is not MoCA-enabled. MoCA-enabled subscriber equipment is intended to operate in response to MoCA signals, and as a result, has the capability of rejecting unwanted MoCA signals when also operating in response to CATV downstream and upstream signals. At the present time, most passive subscriber equipment is not MoCA enabled. Consequently, the problem of the MoCA signals inhibiting the proper functionality of passive subscriber equipment is significant in CATV entry adapters which also conduct MoCA signals in a subscriber premises MoCA network.